This question is definitely related to a resolved thread.
Although this bug is marked as being resolved over a year ago, I have just experienced the same probelem in that the forum documentation states “Under the Forum Management tab in the Forum Module there is a General Preferences link.” and a little further down, “Under the Forum Management tab in the Forum Module there is a Default Permissions link.” when there is in fact no Forum Management tab when setting up the module for the first time as per the instructions in the documentation.
Glad I found the original post describing the problem…